R help - Mar 2009 - Using predict on a biglm object returns NA

Hi R experts,

I used biglm to construct a model (which has categorical variables).

When I run predict on the model output on a new data (for testing) or on the
same data, I get only NA's. I'm able to run predict with some other
models
constructed with biglm. One reason I suspect is that the model itself has a
few undefined terms (NA's). I'm wondering if there's any way to
ignore the
undefined terms (treat them as 0).

Thanks in advance,
Pradheep

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On Fri, 20 Mar 2009, Pradheep K E wrote:
> When I run predict on the model output on a new data (for testing) or on
the
> same data, I get only NA's. I'm able to run predict with some other
models
> constructed with biglm. One reason I suspect is that the model itself has a
> few undefined terms (NA's). I'm wondering if there's any way to
ignore the
> undefined terms (treat them as 0).
No, there isn't.  Well, you can easily get extract the coefficients and do
the same calculations as predict.biglm does -- they aren't that hard. But
the NA means that it wasn't possible to work out from the training data what
the coefficient was, so setting it to zero (rather than, say, 42) doesn't
seem like a reliable strategy. You'd probably be better off refitting a
model that can actually be estimated from the data.


     -thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle